Karen Davranche

Facilitating effects of exercise on information processing

The aim of this study was to examine the facilitating effects of moderate physical exercise on the reaction process to gain a better understanding of the interaction between physiological and cognitive processes. Sixteen participants with specific expertise in decision-making sports performed a double task consisting of choice reaction time while cycling. Signal quality, stimulus–response compatibility and time uncertainty were manipulated. Participants were tested at rest and while cycling at 20% and at 50% of their maximal aerobic power. A mood assessment questionnaire and a critical flicker fusion test were administered before and after the choice reaction time task. The results showed that moderate-intensity exercise (50% maximal aerobic power) improves cognitive performance and that low-intensity exercise (20% maximal aerobic power) enables participants to compensate the negative dual-task effect.

The dual nature of time preparation: neural activation and suppression revealed by transcranial magnetic stimulation of the motor cortex

Single‐pulse transcranial magnetic stimulations (TMSs) of the motor cortex (M1) were performed in order to decipher the neural mechanisms of time preparation. We varied the degree to which it was possible to prepare for the response signal in a choice reaction time (RT) task by employing either a short (500 ms) or a long (2500 ms) foreperiod in separate blocks of trials. Transcranial magnetic stimulations were delivered during these foreperiods in order to study modulations in both the size of the motor evoked potential (MEP) and the duration of the silent period (SP) in tonically activated response agonists. Motor evoked potential area and silent period duration were assumed to reflect, respectively, the excitability of the cortico‐spinal pathway and the recruitment of inhibitory cortical interneurons. Shorter reaction times were observed with the shorter foreperiod, indicating that a better level of preparation was attained for the short foreperiod. Silent period duration decreased as time elapsed during the foreperiod and this decrement was more pronounced for the short foreperiod. This result suggests that time preparation is accompanied by a removal of intracortical inhibition, resulting in an activation. Motor evoked potential area decreased over the course of the short foreperiod, but not over the long foreperiod, revealing that time preparation involves the inhibition of the cortico‐spinal pathway. We propose that cortico‐spinal inhibition secures the development of cortical activation, preventing erroneous premature responding.

Specific effects of acute moderate exercise on cognitive control

The main issue of this study was to determine whether cognitive control is affected by acute moderate exercise. Twelve participants [4 females (VO(2 max)=42 ml/kg/min) and 8 males (VO(2 max) = 48 ml/kg/min)] performed a Simon task while cycling at a carefully controlled workload intensity corresponding to their individual ventilatory threshold. The distribution-analytical technique and the delta plot analysis [Ridderinkhof, K. R. (2002). Activation and suppression in conflict tasks: Empirical clarification through distributional analyses. In W. Prinz & B. Hommel (Eds.), Common mechanisms in perception and action. Attention and performance (Vol. 19, pp. 494-519). Oxford: Oxford University Press.] were used to assess the role of selective response inhibition in resolving response conflict. Results showed that cognitive processes appeared to be differently affected by acute moderate exercise. Reaction time results confirmed that performance is better (faster without change in accuracy) when the cognitive task is performed simultaneously with exercise. Between-trial adjustments (post-conflict and post-error) highlighted that cognitive control adjustments are also fully efficient during exercise. However, the effect of congruency (Simon effect) appeared to be more pronounced during exercise compared to rest which suggests that the response inhibition is deteriorated during exercise. The present findings suggest that acute moderate exercise differently affects some specific aspects of cognitive functions.

Information processing during physical exercise: a chronometric and electromyographic study

Choice reaction time (RT) is shorter when participants perform a choice task at the same time as a sub-maximal exercise than when they are at rest. The purpose of the present study was to determine whether such an exercise affects response execution or whether it alters processes located upstream from the neuro-muscular level. To this end, the electromyographic (EMG) activity of the response agonists was analysed in a between-hand choice RT task performed either concurrently with a pedalling task or at rest. Visual stimulus intensity was also manipulated so as to determine whether exercise further affects early sensory processes. Results shows that exercise affected the time interval elapsing from the onset of the contraction of the response agonists to the mechanical response, thereby indicating that this variable modifies the peripheral motor processes involved in response execution. EMG signal analyses further revealed that the cortico-spinal command is more efficient during exercise than at rest. In addition, exercise was shown to interact with visual stimulus intensity on the time between stimulus and voluntary EMG onset and to increase the critical flicker fusion frequency threshold, thereby indicating that exercise modifies the peripheral sensory processes involved in early sensory operations. The decomposition of RT, with respect to the EMG activity of response agonists, sheds light on the processes affected by exercise and suggests that exercise affects both sensory processes and late motor processes.

Physical exercise facilitates motor processes in simple reaction time performance: An electromyographic analysis

The aim of the current study was to assess the effects of physical exercise on simple reaction time performance. Participants performed a simple reaction time task twice, one time during physical exercise and another time without exercise. Electromyographic signals were recorded from the thumb of the responding hand to fraction reaction time in pre-motor and motor time. The results showed that exercise shortened motor time but failed to affect pre-motor time. This pattern of findings is consistent with previous studies examining the effects of physical exercise on choice reaction time.

Acute incremental exercise, performance of a central executive task and sympathoadrenal system and hypothalamic-pituitary adrenal axis activity

The purposes of this study were to examine the effect of acute incremental exercise on the performance of a central executive task; the responses of the sympathoadrenal system (SAS) and hypothalamic-pituitary-adrenal axis (HPAA) during exercise, while simultaneously carrying out the central executive task; and the ability of Delta plasma concentrations of epinephrine, norepinephrine, adrenocorticotropin hormone (ACTH) and cortisol to predict Delta performance on the central executive task. Subjects undertook a flanker task at rest and during exercise at 50% and 80% maximum aerobic power (MAP). SAS and HPAA activity were measured pre- and post-treatment by plasma concentrations of catecholamines, and cortisol and ACTH, respectively. Reaction time (RT) and number of errors for congruent and incongruent trials on the flanker task showed significant main effects with performance at 80% MAP higher than in the other conditions. RT post-correct responses were significantly faster than RT post-error at rest and 50% MAP but not at 80%. Pre- and post-treatment catecholamines showed a main effect of exercise with a linear increase. Post-treatment ACTH concentrations at 80% MAP were significantly greater than in the other conditions. Delta epinephrine and ACTH combined were significant predictors of Delta RT and Delta norepinephrine was a significant predictor of Delta number of errors. It was concluded that exercise must be at a high intensity to affect performance on the flanker task. Both the SAS and HPAA appear to play a role in the exercise-cognition interaction.

Functional anatomy of timing differs for production versus prediction of time intervals

Timing is required both for estimating the duration of a currently unfolding event, or predicting when a future event is likely to occur. Yet previous studies have shown these processes to be neuroanatomically distinct with duration estimation generally activating a distributed, predominantly right-sided, fronto-striatal network and temporal prediction activating left-lateralised inferior parietal cortex. So far, these processes have been examined independently and using widely differing paradigms. We used fMRI to identify and compare the neural correlates of duration estimation, indexed by temporal reproduction, to those of temporal prediction, indexed by temporal orienting, within the same experimental paradigm. Behavioural data confirmed that accurate representations of the cued interval were evident for both temporal reproduction and temporal orienting tasks. Direct comparison of temporal tasks revealed activation of a right-lateralised fronto-striatal network when timing was measured explicitly by a temporal reproduction task but left inferior parietal cortex, left premotor cortex and cerebellum when timing was measured implicitly by a temporal orienting task. Therefore, although both production and prediction of temporal intervals required the same representation of time for their successful execution, their distinct neural signatures likely reflect the different ways in which this temporal representation was ultimately used: either to produce an overt estimate of an internally generated time interval (temporal reproduction) or to enable efficient responding by predicting the offset of an externally specified time interval (temporal orienting). This cortical lateralization may reflect right-hemispheric specificity for overtly timing a currently elapsing duration and left-hemispheric specificity for predicting future stimulus onset in order to optimize information processing.

Orienting attention in time activates left intraparietal sulcus for both perceptual and motor task goals

Attention can be directed not only toward a location in space but also to a moment in time (“temporal orienting”). Temporally informative cues allow subjects to predict when an imminent event will occur, thereby speeding responses to that event. In contrast to spatial orienting, temporal orienting preferentially activates left inferior parietal cortex. Yet, left parietal cortex is also implicated in selective motor attention, suggesting its activation during temporal orienting could merely reflect incidental engagement of preparatory motor processes. Using fMRI, we therefore examined whether temporal orienting would still activate left parietal cortex when the cued target required a difficult perceptual discrimination rather than a speeded motor response. Behaviorally, temporal orienting improved accuracy of target identification as well as speed of target detection, demonstrating the general utility of temporal cues. Crucially, temporal orienting selectively activated left inferior parietal cortex for both motor and perceptual versions of the task. Moreover, conjunction analysis formally revealed a region deep in left intraparietal sulcus (IPS) as common to both tasks, thereby identifying it as a core neural substrate for temporal orienting. Despite the context-independent nature of left IPS activation, complementary psychophysiological interaction analysis revealed how the functional connectivity of left IPS changed as a function of task context. Specifically, left IPS activity covaried with premotor activity during motor temporal orienting but with visual extrastriate activity during perceptual temporal orienting, thereby revealing a cooperative network that comprises both temporal orienting and task-specific processing nodes.

Does Central Fatigue Explain Reduced Cycling after Complete Sleep Deprivation

PURPOSE Sleep deprivation (SD) is characterized by reduced cognitive capabilities and endurance exercise performance and increased perceived exertion (RPE) during exercise. The combined effects of SD and exercise-induced changes in neuromuscular function and cognition are unknown. This study aimed to determine whether central fatigue is greater with SD, and if so, whether this corresponds to diminished cognitive and physical responses. METHODS Twelve active males performed two 2-d conditions (SD and control (CO)). On day 1, subjects performed baseline cognitive and neuromuscular testing. After one night of SD or normal sleep, subjects repeated day 1 testing and then performed 40-min submaximal cycling and a cycling test to task failure. Neuromuscular and cognitive functions were evaluated during the cycling protocol and at task failure. RESULTS After SD, exercise time to task failure was shorter (1137 ± 253 vs 1236 ± 282 s, P = 0.013) and RPE during 40 min submaximal cycling was greater (P = 0.009) than that in CO. Maximal peripheral voluntary activation decreased by 7% (P = 0.003) and cortical voluntary activation tended to decrease by 5% (P = 0.059) with exercise. No other differences in neuromuscular function or cognitive control were observed between conditions. After SD, mean reaction time was 8% longer (P = 0.011) and cognitive response omission rate before cycling was higher (P < 0.05) than that in CO. Acute submaximal exercise counteracted cognitive performance deterioration in SD. CONCLUSIONS One night of complete SD resulted in decreased time to task failure and cognitive performance and higher RPE compared with the control condition. The lack of difference in neuromuscular function between CO and SD indicates that decreased SD exercise performance was probably not caused by increased muscular or central fatigue.

The role of (dis)inhibition in creativity: Decreased inhibition improves idea generation

There is now a large body of evidence showing that many different conditions related to impaired fronto-executive functioning are associated with the enhancement of some types of creativity. In this paper, we pursue the possibility that the central mechanism associated with this effect might be a reduced capacity to exert inhibition. We tested this hypothesis by exhausting the inhibition efficiency through prolonged and intensive practice of either the Simon or the Eriksen Flanker task. Performance on another inhibition task indicated that only the cognitive resources for inhibition of participants facing high inhibition demands were impaired. Subsequent creativity tests revealed that exposure to high inhibition demands led to enhanced fluency in a divergent thinking task (Alternate Uses Task), but no such changes occurred in a convergent task (Remote Associate Task; studies 1a and 1b). The same manipulation also led to a hyper-priming effect for weakly related primes in a Lexical Decision Task (Study 2). Together, these findings suggest that inhibition selectively affects some types of creative processes and that, when resources for inhibition are lacking, the frequency and the originality of ideas was facilitated.